I make a compost pile that is 4 feet by 4 feet by 4 feet in the fall and by spring it will have been digested to a 2 x 2 x 4 pile of compost. The link below may be of some help also.

Here is a link that might be useful: Composting Tutorial

If this is your first foray into intentional composting you'll be surprised at how much it shrinks. Count on that. And it continues to shrink over several years so would need to be replaced yearly to maintain depth in your bed. I imagine plywood bottom will rot fast, too... and use N from your soil to do that.

I know nothing about sq ft gardening but can't help but wonder what you plan to grow there? veggies? flowers?
6" deep soil is pretty shallow...

Looks like a lot of that gravel could be sifted out through a framed 1/4" or 1/2" hardware cloth screen. Have you tried that?

Karen

Textbook case of building a compost pile! She's a beauty.

I'm gonna say a 60% reduction in volume because the leaves were mostly not shredded from what I can tell. And I'd keep the "leftovers" to add to the top as the pile settles.

Good job. I'm going to bookmark this thread to give to anyone that asks me how to build a batch CP.

Lloyd

Nice!! I have to rebuild some bins which are falling apart...

@kqcrna, in Square Foot Gardening you don't use dirt, you use the mix:

1/3 good compost
1/3 peat moss
1/3 vermiculite

Good compost has it's own recipe:
no more than 20% of any single ingredient:
straw, hay, leaves, grass, old sod, spoiled garden produce, peels, newspaper, eggshells, manure, tea bags.

And no more than 10% of these:
corn cobs, shredded twigs or bark, pine needles, hedge trimmings, wood shavings, sawdust, coffee grounds, peanut shells.

The books goes into much more detail and includes strategies on purchasing compost (get a variety) and vermicomposting.

Since the good compost is readily available the roots don't need to go so far to hunt out nutrients. Root plants like potatoes and carrots go into a 12" deep box.

I have removed so many rocks from that garden already, we actually covered a path in a different area 3'x8'. This spring that section in the picture was all cleared of rocks and tilled 18" deep.

We also have a Walnut tree nearby and the plywood is to keep the roots out. I'm told Walnut trees kill off other plants, particularly Tomatoes. I'll probably treat the wood with linseed oil and charcoal.

@kimmsr Thanks for the link, I'll look it over.

@Lloyd Thanks for the kind words.

So you're going to grow tomatoes in 6" mix, and with a plywood floor under it???

Karen

A 6 inch box will work great for tomatoes I might skip the plywood but I was really surprised helping my sister build a square foot box that the book had you seal the bottom with landscape fabric
I can't remember was it the roots or leaves of the walnut that caused problems? others here know

A really nice looking compost pile hope she heats up real well for you I would guess it reduces about half

There is a square foot forum here on gardenweb if you haven't already found it

A few days in I felt the pile through the tarp on top, I could feel some good heat. The top of the tarp has cooled down since.

Because of daylight saving time I was able to have light to turn the pile in the morning today. It's been 9 days since the pile was built.

I used a flat-tined fork to do most of the work. it was quite smelly at times. There was no wind at all so the fumes wafted into my face. Not good, once the smell was intense enough that I actually could taste the fermenting horse poo. Yuk.

The pile is looking quite nice. The interior was very hot, I could feel it radiating. It steamed nicely.

While turning it my less-than-enthusiastic son sprayed the pile with water and occasionally broke up the chunks.

A few years ago I adjusted the plumbing so I could have hot water outside, this was for the kids to play in the sprinkler on slightly cooler days. Didn't think it would be so handy for the compost.

This is the original pile with the wire removed. It had sagged about 3 inches within the enclosure over 9 days.
{{gwi:310166}}

You can see the steam. You can also see the lack of wind. I wish there was a little, the smell hurt.
{{gwi:310168}}

On Halloween I added a large amount of pumpkin guts with seeds. These seeds sprouted. Pretty cool! They are now deep in the pile so they will die. I guess these seeds are now officially called "malted pumpkin seeds". Anyone make whiskey out of these ever?
{{gwi:310169}}

Here is after turning. The pile is a lot smaller, probably 20% loss.
{{gwi:310171}}

I would not use a plywood bottom. To keep tree roots out but not harm drainage in the bed, I would use landscape fabric on the bottom. But question for you: is that gravel base full of tree roots? If no, then you don't need to worry about the tree roots at all. I would still use landscape fabric to discourage mixing of the good topsoil with all that gravel.

No, there are not roots in there currently. I'm thinking the plywood isn't necessary. I will put fabric down instead.

A plywood bottom would have many holes drilled for drainage though.

For what it's worth, I don't think I'd even bother with the landscape fabric at the bottom of your beds. I put my raised veggie garden over the top of what used to be lawn. I framed out the beds at 12" deep and just set them down over the dead grass. Under that grass is a couple inches of top soil with a couple inches of gravel under that. Under that is the black clay they call "soil" around here.

In any event, I've got a layer of gravel under my beds and it's doing no harm. I do occasionally dig up a few rocks when I'm turning in compost and manure, but not much and I pull them out when they come up. (I figure in about 40 years of turning I'll be rock free.) And by leaving the bottom "open" if I'm planting something that has strong deep tap roots, they'll have a place to go.

Just another idea....

In a bed 12 (14?) inches deep you would not turn up much gravel, but the OP plans a bed only 6 inches deep.

Rabbit manure is the best & if you are not getting 8-10 pounds of waste from your rabbit, then you are not feeding them. Rabbits will eat any thing green. Rabbit manure is the highest in Nitrogen 2.4%,phosphate 1.4, 2nd highest in potash 0.6 , sheep manure has 0.9 potash. Chicken is next 1.1% Nitrogen.
But peanut shells have 3.6% n,.70 phos,.45pot.Coffee waste has 1.45 or 2.0% n,00phos,2.00. I mean to say manure is good, but do not over look the plants that have good stuff too.

What you call an "unintentional" compost pile is my compost pile. Toss and go.

Did the sneaker ever decompose? (Yes, I'm just joking.) ;)

After a long, long winter we have finally thawed in Minnesota. Where's all this warming they are promising?

Today I turned the piles for the third time and added 7 buckets of scraps. I also added some beneficial bacteria and trace minerals. I was glad the horse poo smell/taste was gone.

There were some chunks of frozen compost embedded in the chicken wire so I had to go with a straight pile instead of an enclosed, neat pile.

I'm going to add just a little more then work it often so it's ready for use on May.

I saw another article title talking about bread from a bakery, great idea! I'll have to stop by the one down the street to see if I can get their throw-outs. I just love the squishy whole loaves after they get wet in the compost pile.

ooooooh, I can't wait to see what annpat says about the bread on this one. :)

But mctoon, have to say I found that fermented horse manure taste quite hilarious. poor thing!

Kim